How about something to do with emails such as how to send an email to lots of people without each one knowing who else is on a mailing list or how to send attachments. There're probably more email type topics which can be covered.

From what angle are you referring to with the "without each one knowing who else is on a mailing list"? As in a mailing list program administrator that's taking the emails from a file, or as a feedback form to sent to multiple recipients?

Presumably a mailing list or mulitple mailing recipients comes from a file somewhere. I read conflicting arguments about whether or not blind copy works and what the maximum number of multiple recipients should be. In some cases you want the recipients to know who else has been sent the same email (probably in a workplace environment) but in other cases you don't (club membership or retail environment).